1. Field of the Invention
The invention relates in general to articulated arms for use in coordinate measurement machines (CMMs) and in particular to an articulated arm having an on-board processor and display for operation independent of a host computer.
2. Prior Art
FIG. 1 is a diagrammatic view of a conventional three dimensional measuring system generally including a coordinate measuring machine (CMM) 10 composed of a manually operated multijointed arm 12 and a support base or post 14, a controller or serial box 16 and a host computer 18. It will be appreciated that arm 12 electronically communicates with serial box 16 which, in turn, electronically communicates with host computer 18. Additional detail of the conventional three dimensional measuring system can be found in U.S. Pat. No. 5,402,582, the contents of which are incorporated herein by reference.
Currently, articulated arms are provided as a system with a host computer and applications software. The articulated arm is commonly used to measure points on an object and these measured points are compared to computer-aided design (CAD) data stored on the host computer to determine if the object is within the CAD specifications. In other words, the CAD data is the reference data to which actual measurements made by the articulated arm are compared. The host computer also contains applications software that guides the operator through the inspection process. In many occasions for complicated applications this arrangement is appropriate since the user will observe the three-dimensional CAD data on the host computer while responding to complex instructions and using complex commands in the applications software.
Current applications software also allows the user to write specific programs or executables in a learn mode which is then used by a far less trained individual in an execution mode to perform a pre-prescribed set of measurements of an object. The result is that the final usage of the articulated arm is highly simplistic in that an assembler or mechanic is instructed by the software prompts to position the probe at known locations and acquire the three-dimensional data. In this case, during the execution phase, the use of the high level host computer and application software is completely inappropriate and adds unnecessary costs.
Another drawback to conventional systems is that the measured data is not compared to the reference data (e.g. CAD data) in real time. Because the arm 12 has no processing capability, the measured or actual data must be transferred to the host computer 18 where it is compared to the reference (e.g. CAD) data to determine if the object meets the reference specifications. If the result of the comparison is not favorable, then the operator must be notified and the object may need additional measurement. This communication back and forth between the arm and the host creates unnecessary delay.